Pill resistant polyester fabrics



United States Patent U.S. Cl. 16189 12 Claims ABSTRACT OF THE DISCLOSUREA process for the preparation of pill resistant woven and knittedfabrics and the products produced thereby, said fabrics containing atleast 25% by weight of nonfusible polyethylene terephthalate staplefibers having an intrinsic viscosity in excess of 0.46, pill resistancebeing achieved by incorporating fusible polyethylene terephthalatestaple fibers into the blend and then heating the finished fabric tofusion temperatures.

This application is a continuation of Ser. No. 414,403 filed Nov. 27,1964 and now abandoned.

This invention relates to fabrics resistant to pilling. Moreparticularly, the invention is directed to fabrics made out of blends ofwholly or substantial amounts of staple polyethylene terephthalatefibers which have improved pill resistant properties and to processingtechniques to provide said fabrics.

As is well known, it is common in all fabrics which are made, yarnspossessing a hairy or Wooly surface form pills. Pilling results whenloose fiber ends escape from yarns and the loose ends, especially at thepoints where the fabric is exposed to rubbing, collect on the surface ofthe material and ball up into rather unsightly fluffs. With woolenfabrics, pilling has presented no serious problems since the pills arevery loosely held and either fall off or are unconsciously brushed offbefore there is a serious accumulation. The difiiculty with fabrics madeof substantial amounts of polyethylene terephthalate lies not in thefact that pills are formed but they cling tenaciously and cannot bebrushed off but require pulling off with effort. These pills tend toaccumulate and provide an unsightly appearance resulting inembarrassment to the wearer of the clothing.

In Belgian Patent 548,150, Eggleston et al., granted Nov. 20, 1956, andassigned to Imperial Chemical Industries Limited, London, England, apartial solution to the pilling problem for polyethylene terephthalatefabrics was proposed. It was suggested that fabrics be made from highlycrystalline polyethylene terephthalate staple fibers having a lowmolecular weight and having an intrinsic viscosity in the range fromabout 0.28 to about 0.45. It was discovered that the tendency forpilling of polyethylene terephthalates having low molecular weights asdescribed was eliminated or at least reduced considerably. However, thefabrics containing polyethylene terephthalate staple fibers havingintrinsic viscosities in excess of about 0.46 still possessed theundesirable pilling problem. Chemical treatments and chemical additivesare additional proposals recommended to overcome the pilling problems ofthe polyethylene terephthalate fabrics but a different hand of thefabrics are obtained over that of the untreated fabric which isgenerally not desirable.

It is the object of this invention to provide pill resistant textilefabrics containing substantial amounts of high .molecular weightcrystalline polyethylene terephthalate staple fibers without utilizing achemical treatment or chemical additive to provide the desired result. Afurther object is to provide a unique process for providing pillresistant polyethylene terephthalate fabrics of the type describedabove. These and other objects will become apparent to those skilled inthe art by the reading of the following detailed disclosure and claims.

The objects of the invention are attained by initially producing ablended yarn containing at least about 25 weight percent of polyethyleneterephthalate staple fibers which are crystalline having an intrinsicviscosity in excess of 0.46, and non-crystalline, fusible polyethyleneterephthalate staple fibers in amounts ranging from about 5 to about 25weight percent of said blend. The blended yarns are woven or knittedinto the desirable fabric-like construction and exposed to elevatedtemperatures which will not detrimentally affect the fiber content for aperiod of time to fuse the non-crystalline polyethylene terephthalatefibers. The resulting fabric obtained provides a dramatic improvement inpilling resistance and at the same time does not substantially alter thehand of the finished fabric when compared to the regular high pillingfabric.

The initial fabrics prepared for treatment to obtain the finishedfabrics of this invention are woven or knitted from yarns made fromblends of various staple fibers of polyethylene terephthalate fiberswith other synthetic staple fibers, natural occurring staple fibers orcombinations thereof.

One of the ingredients of the yarn used to prepare the initial fabricincludes at least about 25 percent by weight of highly crystallinepolyethylene terephthalate staple fibers having an intrinsic viscosityin excess of 0.46. These fibers and preparation thereof are well knownin the art and are also known to provide undesirable pilling propertieswhen used in fabrics. The polyethylene terephthalate fibers as usedherein can include the homopolyester of ethylene glycol and terephthalicacid as well as the copolymers of polyethylene terephthalate whichinclude additional components such as isophthalic acid, phthalic acid,naphthalic acids, bibenzoic acids, combinations thereof, sulfonatedproducts thereof and the like.

A further essential ingredient of the yarn used to prepare the initialfabric includes about 5 to 25 weight percent of the blend ofnon-crystalline, fusible polyethylene terephthalate homopolymer orcopolymer stable fibers. For this fiber, the intrinsic viscosity is notessentially critical. It is well known in the art that polyethyleneterephthalate fibers require a high degree of crystallinity to providethe desirable physical properties such as tenacity, elongation, etc.needed to produce the desired fabrics from said fibers. One method ofproducing a high degree of crystallinity is to stretch the fiber about1.5 to about 8 times, or higher, its original length above the secondorder transition temperature. The resulting fiber will be essentially anon-fusible fiber up to the melting point of the polymer. For thisinvention, however, a specific amount of fusible polyethyleneterephthalate staple fibers is required to obtain the desired result ofimproved pill resistance in the fabric. Fusible or non-crystallinepolyethylene terephthalate fibers can be produced by merely spinning thepolymer to form fibers. These fibers have a low crystallinity, lowtenacity, high elongation, high dye uptake, low birefringence, amongothers, corresponding essentially to the opposite properties of thehighly crystalline fibers used herein. These non-crystalline fibers canbe produced by partially drawing or collecting directly from the meltspinning operation. In any event, it is essential that a portion of thefiber used in the blend to produce the fabrics of this invention must befusible at elevated temperatures. The preferred amount of fusiblepolyethylene terephthalate staple fibers ranges from to about weightpercent of the blend. It has been found that if the amount of fusiblepolyester fiber is increased to 30 weight percent of the yarn, thefabric .made therefrom does not have the desired high pill resistance.

The yarns utilized herein cannot only consist of crystalline ornon-fusible and non-crystalline or fusible polyethylene terephthalatestaple fibers only to provide the desired fabric effects but can includeadditional components such as other synthetic fibers such as nylon,acrylics, acetate, and the like, as well as naturally occurring fiberssuch as cotton, wool and the like. These additional components are addedin amounts so that an acceptable fabric can be obtained and can rangefrom about 50 to about 70 percent by weight, preferably in the rangefrom 30 to about 60 weight percent. The preferred components are wooland cotton in combination with polyethylene terephthalate which havebeen fibers found highly acceptable for fabric uses.

After the above-described yarns are prepared, they are woven or knittedinto fabrics. These fabrics are then exposed to elevated temperatures inthe range from about 200 F. to below the melting point of the lowestmelting component of the fabric for a period of time sufiicient to causethe non-crystalline polyethylene terephthalate staple fibers to fuse.Care is taken in the heating process to avoid damaging anyone of thecomponents in the fabric. Although it is not definitely known, thefusion of the noncrystalline fibers is believed to anchor the individualfibers of polyethylene terephthalate or other components in the fabricin a binding manner thereby making the fabric less prone to pill withuse.

The preferred method for fusing the non-crystalline polyethyleneterephthalate in the fabric is to calender the fabric at temperatures inthe range from about 200 F. to about 260 F. The calendering process iswell known in the art and can be carried out by passing the fabricbetween rollers under pressure on the calender frame. The number ofrollers may vary from two to seven depending on the desired finish ofthe fabric. The fabric can be passed over the rollers three or fourtimes depending on the particular finish sought. The finish may be dull,flat, glazed, watered, or moir smooth. The pressure and heat of therollers are the important factor in obtaining the desired finish.

The following examples will demonstrate the present invention withoutlimiting the same:

EXAMPLE 1 Yarns of a staple fiber blend containing varying amounts offusible and non-crystalline polyethylene terephthalate and the remainderstaple fibers made of nonfusible polyethylene terephthalate having anintrinsic viscosity of 0.6, were prepared. The yarns were used toconstruct Swiss piqu fabrics to promote pilling, i.e. short staple, lowtwist, loose knit. After the fabric was prepared, the fabric wascalendered at 250 F. in order to fuse the non-crystalline polyethyleneterephthalate fibers. The calendering must be effected before the fabricis subjected to temperatures above its second-order transitiontemperature (about 170 F.) under conditions which allow shrinkage (e.g.dyeing). After calendering, the fabrics are very stiff but themechanical working during dyeing and fiinshing softens the fabricsconsiderably to provide a desirable hand of the finished product. Thefabrics were then exposed to a Random Tumble Pilling Test which includesthe placing of the fabrics in a tumbler with abrasive paper for aspecified period of time and count the resulting pills. The followingresults were obtained in Table I below:

TABLE I Yarn composition Percent non- Fabric-Random tumble Percentfusible fusible pilling test polyethylene polyethylene terephthalateterephthalate 10 minutes 20 minutes EXAMPLE 2 Fabrics were woven in amanner to incorporate a special blended yarn as described below in thefilling portion and utilizing a yarn made of a blend of 55 percent byweight of non-fusible polyethylene terephthalate (intrinsic viscosity0.58) and 45 percent wool staple of the worsted quality. All the yarns,4; wool-cotton yarn count) utilized had Z type twist of 13.7 turns perinch. After the fabric was woven, the fabric was calendered at 250 F.prior to dyeing and finishing in order to fuse the non-crystallinepolyethylene terephthalate fibers. The fabric was then submitted to thevarious tests with the following results:

Pilling fiber composition 20% fusible polyethylene 55% non-fusibleterephthalate polyethylene staple fiber, terephthalate 35% non-fusiblestaple fiber and polyethylene 45% wool staple terephthalate staplefiber, Tests 45% wool staple Grab tensile:

Warp 104 204 Filling 173 Flex abrasion, cycles to finish. 2, 500+ 2,500+ Flat abrasion, cycles to first thread break 512 l, 007 Randomtumble pilling: 1

30 minutes 2 5 60 minutes 1 5 Brush and sponge pilling: 1

10 minutes 1 4 20 minutes 4 Wash and Wear rating 4-5 4-5 I The ratingsof these tests are on a basis of 1 to 5 where 5 is the best rating and 1the poorest rating while the intermediate numbers represent varyingdegrees of bad (2) to good (4).

These results clearly indicate that the use of fusible polyethyleneterephthalate in blends provides, under certain conditions, improvedpill resistance as well as fiat abrasion cycles to first thread break.In a similar manner as described above, cotton staple blended withpolyethylene terephthalate in place of wool staple would provide similarresults as utilized under the conditions of this invention.

EXAMPLE 3 Various yarns were blended to determine the effect of knittedfabrics in regard to pilling effects. Yarns were blended in thefollowing manner:

The yarns 1) and (2) /gr) wool-cotton yarn count) were individuallyknitted into fabrics. The fabric (2) was then exposed to calendering at250 F. to fuse the fusible and non-crystalline polyethyleneterephthalate fibers. The finished fabrics were then exposed to varioustests with the following results:

The tests and'ratings are identical to those described in Example 2. Inthe knitted fabrics, the fabrics of this invention (2) show improvedresults in pilling resistance over the blends of regular non-fusiblepolyethylene terephthalate fabrics.

It is to be understood that the foregoing description is merelyillustrative of preferred embodiments of the invention of which manyvariations may be made by those skilled in 'the art within the scope ofthe following claims without departing from the spirit thereof.

Having thus disclosed the invention, what is claimed is:

1. A woven or 'knitted textile fabric having a high resistance topilling prepared from a yarn comprising a blend of at least about 25percent by weight of said blend of non-fusible polyethyleneterephthalate staple fibers having an intrinsic viscosity in excess of0.46, about to about percent by weight of said blend of fusiblepolyethylene terephthalate staple fibers and the remainder of said blendof staple fibers selected from the group of synthetic fibers and naturalfibers, wherein said fusible polyethylene terephthalate staple fibersare fused in fabric form.

2. The textile fabric of claim 1 wherein the natural fiber is wool.

3. The textile fabric of claim 1 wherein the natural fiber is cotton.

4. A woven or knitted textile fabric having a high resistance to pillingprepared from a yarn comprising a blend of about 75 to 95 percent byweight of said blend of non-fusible polyethylene terephthalate staplefibers having an intrinsic viscosity in excess of 0.46 and about 10 toabout 20 percent by weight of said blend of fusible polyethyleneterephthalate staple fibers wherein said fusible polyethyleneterephthalate staple fibers are fused in fabric form.

5. A woven or knitted textile fabric having a high resistance to pillingprepared from a yarn comprising a blend of about 80 to about 90 percentby weight of said blend of non-fusible polyethylene terephthalate staplefibers having an intrinsic viscosity in excess of 0.46 and about 10 toabout 20 percent by weight of said blend of fusible polyethyleneterephthalate staple fibers wherein said fusible polyethyleneterephthalate staple fibers are fused in fabric form.

6. A woven or knitted textile fabric having a high resistance to pillingprepared from a yarn comprising a blend of about to about 50 percent byweight of said blend of non-fusible polyethylene terephthalate staplefibers having an intrinsic viscosity in excess of 0.46, about 10 toabout 20 percent by weight of said blend of fusible polyethyleneterephthalate staple fibers, and about 30 to about 60 percent by weightof said blend of wool staple fibers wherein said fusible polyethyleneterephthalate staple fibers are fused in fabric form.

7. A process for increasing the pill resistance of a woven or knittedtextile fabric prepared from a yarn comprising a blend of at least 25percent by weight of said blend of non-fusible polyethyleneterephthalate staple fibers having an intrinsic viscosity in excess of0.46, about 10 to about 20 percent by weight of said blend of fusiblepolyethylene terephthalate staple fibers and the remainder of said blendof staple fibers selected from the group of synthetic fibers and naturalfibers, comprising heating said fabric at temperatures in the range fromabout 200 F. to below the melting point of the lowest melting componentof said fabric for a period of time sufiicient to cause fusion of saidfusible polyethylene terephthalate fibers.

8. A process for increasing the pill resistance of a woven or knittedtextile fabric prepared from a yarn comprising a blend of at least 25percent by weight of said blend of non-fusible polyethyleneterephthalate staple fibers having an intrinsic viscosity in excess of0.46, about 10 to about 20 percent by weight of said blend of fusiblepolyethylene terephthalate staple fibers and the remainder of said blendof staple fibers selected from the group of synthetic fibers and naturalfibers, comprising heating said fabric at temperatures in the range fromabout 200 F. to 260 F. for a sufficient period of time to cause fusionof said fusible polyethylene terephthalate fibers.

9. The process of claim 8 wherein the natural staple fiber in the blendis wool.

10. The process of claim 8 wherein the natural staple fiber in the blendis cotton.

11. The process of claim 8 wherein the yarn blend is composed of aboutto percent of non-fusible polyethylene terephthalate staple fibershaving an intrinsic viscosity in excess of 0.46.

12. The process of claim 8 wherein the yarn blend contains about 30 to50 percent by weight of non-fusible polyethylene terephthalate staplefibers having an intrinsic viscosity in excess of 0.46, about 10 to 20percent by weight of fusible polyethylene terephthalate staple fibersand about 30 to about 60 percent by weight of wool staple fibers.

References Cited UNITED STATES PATENTS 3,203,847 8/1965 Harwitz 161-92FOREIGN PATENTS 808,287 2/1959 Great Britain. 899,263 6/ 1962 GreatBritain.

OTHER REFERENCES Dupont Textile Fibers Technical Information, Da cronPolyester Fiber, Bulletin CSB-D-35, July 1954, Suggestions For Reducing,Pilling & Fuzzing of Spun Fabrics, pp. 3, 5, 8, T erylene Digest.

ROBERT F. BURNETT, Primary Examiner J. D. FOSTER, Assistant Examiner US.Cl. X.R.

